It's a very good idea to read through the following files available in Packages > Default >

Preferences.sublime-settings

Default (your OS).sublime-keymap

and maybe *.sublime-menu

A lot of functionality is only "documented" in these files.

There are many plugins (called "packages") which enhance and extend Sublime. Although it's very easy to try out new plugins (via Package Control), I'd recommend removing or disabling what you don't use routinely, to maintain Sublime lean and fast. There's a nice list of some of the most popular plugins here: https://github.com/mrmartineau/SublimeTextSetup